Despite being regarded as one of the world’s best strikers, Guardiola chose to name Sergio Aguero on the bench at the Nou Camp and even though City trailed at half-time he didn’t bring him on until 14 minutes from the end when the game was lost.

Guardiola claimed his decision was a tactical one to allow him to play an extra midfielder to try to nullify Barca’s famed passing game.

Until goalkeeper Claudio Bravo was sent off, the move appeared to have worked with City having plenty of possession and carving out several good chances.

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Sergio Aguero was left on the bench for Manchester City's Champions League clash with Barcelona

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Sergio Aguero was brought on by Pep Guardiola at the Nou Camp in the second half

Although Guardiola says Aguero – who was also on the bench against Everton at the weekend – accepted his surprise demotion with good grace, privately the striker was fuming at what he regards as a major snub and it is understood there are tensions between the pair. Significantly, Aguero didn’t join the warm-up in the Nou Camp.

Guardiola has repeatedly asked for more work off the ball from Aguero this season despite his impressive goal return of 11 in his first nine appearances of the season before the visit to the Nou Camp.

Aguero has admitted he is still adapting to Guardiola’s demands and while on Argentina duty last week admitted the demanding City boss is “picky about everything”.

He has two years left on his contract and is said to have agreed in principle a one-year extension in the summer, but that has still not been formally announced amid suggestions Aguero may be having second thoughts about making a long-term commitment.

Manchester City head to Barcelona in new 'travelling attire'

Tue, October 18, 2016

Manchester City caused a stir when they headed off to their Champions League clash with Barcelona in new travelling attire consisting of matching bomber jackets, shirts, ties, jeans and white trainers

Manchester City have been showing off their new 'travelling attire' as they head off to Barcelona for tomorrow night's Champions League clash, but what do you think of the Citizens' slick new threads?

Some sources at City are convinced Aguero – signed from Atletico Madrid for a then club-record £38million in 2011 – will be on his way at the end of the season and that is bound to alert top clubs both in the Premier League and abroad, especially Bayern Munich.

Guardiola has shown with his treatment of Hart, Toure and Nasri that he is not afraid to purge big names and crowd favourites. Hart and Nasri are now on loan at Torino and Sevilla respectively while Toure is still at City but has been completely frozen out.

Signficantly, City’s new £27million striker Gabriel Jesus will arrive from Palmeiros at the end of the Brazilian season in December with the Olympic Gold mediallist set to provide serious competition for Aguero, who has always been an automatic choice.

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Skipper Vincent Kompany must also be fearing for his future after being left out of the squad of 18 for the Barcelona game despite being fit again. City could have done with his experience, composure and leadership as they made mistakes that led to all four of Barcelona’s goals.

The biggest worry for Guardiola is that his team have now conceded 10 goals in a run of four winless games – the first time in his managerial career he has gone four games without a victory. What has been underlined in recent games is City’s need for two new full-backs and a centre-half, if Guardiola no longer trusts 30-year-old Kompany to stay fit.

Guardiola has backed new keeper Bravo even though he seems to have unsettled City’s defence at a time when Hart has recovered his best form for Torino and England.

The only mitigation the Chile international can have for his inexplicable mistake in the Nou Camp is that he is under orders from Guardiola to play the ball out rather than hoof it clear. It is risky and mistakes will happen.

He has already gifted Zlatan Ibrahimovic a goal in the Manchester derby and was lucky not to be sent off later in the game for a desperate lunge at Wayne Rooney after mis-controlling the ball.

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Kelechi Iheanacho led the line for Man City against Everton at the weekend

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Nolito was selected ahead of Aguero to add more muscle in the midfield

After winning their first 10 games of the season, the wheels have suddenly come off for City but Kevin De Bruyne says they must keep faith with Guardiola’s tactical blueprint.

De Bruyne, who operated as a ‘false No9’ with Aguero the bench, said: “This is the way we need to play and we’ll win a lot of games like this. It’s the right way.

“Obviously, against Everton, we could have won easily, everyone knows that, even if it was 1-1. Even against Barcelona we didn’t play badly, we just made mistakes, which happens. We could have scored goals, we had the same amount of possession, and almost the same amount of goalscoring opportunities.

“In the end they scored four and it looks bad, but I don’t think we should feel bad. I don’t think we have to change as a team or change the mentality. We’ve already won a lot of games, and it’s not like Barcelona are a bad team.”

During their flying start to the season Guardiola always insisted there was still much work to do before City are what he wants. The nightmare in the Nou Camp only served to underline the task.